Your quote: At key evolutionary junctures in the Soul’s life in which the Soul intends to liberate from its past, to embrace and act upon the thought forms that correlate to its own master blueprint for the entire life, the Soul will ignite thought forms to the current life ego, conscious awareness, that have a repetitive nature to them. In essence these thought forms that correlate to the Soul’s next evolutionary steps will repeat over and over in order to get the attention by way of the ego that the Soul has created in the current life. It is these repetitive messages that the Soul, by way of the ego created, needs to act upon in order to evolve: to liberate from the past that binds it. These repetitive messages are just that: repetitive versus thought forms, ideas, that appear at random and have no repetitive occurrence.

It has been taught that the repeating thoughts/awareness activated by important Uranus transits are relevant to one's approaching future.

I was wondering whether the repeating thoughts/messages/awareness activated by the transit of Uranus could pertain to dynamics or incidents that took place in past lives since all the memories of past lives exist within the Soul? Specifically, that one is "seeing" a theme play over and over in one's mind. Could this be something that actually happened in a past life?

For example, Composite natal stellium of South Node-Jupiter-Uranus in Cancer in the 9th house being squared by transiting Uranus in Aries in the 6th house

Repeating message or repeating theme from past life being activated by Uranus transit: Sudden loss or sudden ending of relationship - with corresponding emotional dynamics - because one partner had a need for freedom, or desired to end the relationship, or just simply took off, or sudden separation due to a cataclysmic event.

In order to evolve, there is a need to act upon the repeating messages by changing the emotional dynamics of the past, that are repeating in the current life. This also means changing the philosophical framework of the relationship via analysis/insight to those principles in line with Natural Law and communicating this through the North Node Capricorn 3rd where, perhaps, a commitment or clear understanding could be communicated between the couple.

So if one is receiving repeating thought forms, let's say, that the relationship will suddenly end, can the evolutionary requirement to evolve take place through consciously changing the emotional structures, or does the incident of sudden loss need to take place again, repeat, for that to happen?

Those repeating messages linked with prior memories of the ending of the relationship due to emotional issues would have to be accompanied with repeating messages of what new types of emotional dynamics to try to move towards if the relationship is to last, and reflect the archetype of the Uranus transit. Remember too that Uranus correlates with 'long term memories' which can also mean the memories of other lifetimes. So, yes, when the Uranus transit is active such memories can manifest within the conscious awareness of the Soul by way of it's ego in the current life. Yet, at the same time, the messages from the Soul by way of Uranus would also contain the strategies or ways to evolve beyond the past memories that would have a repeating nature.